About 1 million cubic metres of mud buried dormitories and homes owned by the Shaanxi Wuzhou Mining Company in Shanyang county early on Wednesday.
Officials said 14 people had been rescued, the operations had been greatly hampered by heavy rain.
China has seen severe weather during the current monsoon season.
The powerful Typhoon Soudelor hit southern China over the weekend bringing strong winds and rain,.
Shanyang officials said the authorities were alerted to the landslide at 01:47 local time (17:47 GMT on Tuesday).
Fifteen dormitories and three residential buildings were buried, trapping at least 40 people initially.
The local government said on its website that people in the area surrounding the landslide had been evacuated, and that large machinery and rescue personnel had been brought in.
State broadcaster CCTV said dozens of soldiers, some with sniffer dogs, were at the scene looking for signs of life.